Preparation of 1,4-dienes of high trans-isomer content

ABSTRACT

1,4-Dienes of high trans-isomer content are prepared by contacting ethylene with a 1,3-diene in the presence of a catalyst system comprising an organic solvent-soluble organonickel compound in which the nickel is zerovalent or divalent, a hydrocarbylaluminum chloride or bromide, and an aryl phosphinite. Optionally, the catalyst system may also contain a heteroorganoaluminum compound.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for preparing 1,4-dienes of hightrans-isomer content.

2. Description of the Prior Art

Sulfur-curable elastomeric copolymers of α-olefins with nonconjugateddienes are well known. Particularly important are terpolymers ofethylene, propylene and a nonconjugated diene comonomer having only onepolymerizable double bond. Such terpolymers are known in the industry asEPDM elastomers. The nonconjugated diene comonomer generally is a1,4-diene such as 1,4-hexadiene. Terpolymers of this type are findingincreased use, for instance, in manufacture of molded automobile parts,transmission belts, hoses, and the like.

1,4-Dienes can be prepared by several processes, including the catalyticaddition of an α-olefin to a conjugated diene. U.S. Pat. No. 3,306,948,to Kealy discloses such a catalytic process. In this process thereactants are contacted in the presence of a catalyst made from at leasttwo moles of an organometallic compound and one mole of a nickelcompound containing at least one monodentate trivalent phosphorus ligandsuch as tributylphosphine. The organometallic compound can be, forexample, an aluminum alkyl, an aluminum aryl, or an organoaluminumhalide.

Although these processes give high yields of 1,4-dienes, they aredeficient in that 1,4-diene products of low trans/cis isomer ratio,generally about 2:1 to at most 3:1, are obtained. Trans-1,4-dienes aremuch more desirable monomers for the EPDM elastomer synthesis becausethey give straight chain copolymers of good physical properties andsufficient unsaturation for sulfur vulcanization. The cis isomers giveless unsaturated copolymers, thus rendering the copolymers lessattractive commercially.

U.S. Pat. No. 3,565,967, to Collette and Su discloses a process forobtaining 1,4-dienes having a trans/cis-isomer ratio of at least 4:1. Inthis process ethylene is contacted with a 1,3-diene in the presence of asoluble zerovalent or divalent nickel compound, an organoaluminumchloride or bromide, and a tertiary phosphine ##STR1## WHERE A is thenaphthyl radical, B is either a C₁ -C₆ alkyl or the allyl radical, D iseither the phenyl or a substituted phenyl radical, m+ n+ p= 3, each of mand n independently can be 0, m cannot be larger than 1, while p cannotbe smaller than 1, provided that when D is pentafluorophenyl,pentachlorophenyl, or tetramethylphenyl, then p must be 1. Furtherincrease in the trans/cis ratio can be obtained by the addition of analuminum compound of the structure (R₁)_(a) AlZ_(b) where R₁ is analkyl, cycloalkyl or aryl radical having 1-12 carbons, and Z is --OR₂,--N(R₃)(R₄) or =N(R₅) where each of R₂, R₃, R₄, and R₅ can be an alkyl,cycloalkyl, aralkyl, or aryl radical having 1-12 carbons; when Z is=N(R₅), R₁ can also be hydrogen; each of a and b is either 1 or 2, andthe sum of a+ b is 3; except that when Z is =NR₅, each of a and b is 1,and a+ b is 2. The preferred phosphine, (C₆ H₅)₂ PC₆ F₅, is relativelyexpensive and its use generally leads to slower reaction rates. It wouldbe desirable to find a catalyst component which gives more rapidreaction and is less expensive than the tertiary phosphine.

SUMMARY OF THE INVENTION

It has now been discovered that 1,4-dienes of high trans-isomer contentcan be prepared by the process which comprises contacting ethylene with1,3-diene of the formula

    CH.sub.2 =C(R.sup.1)CH=CHR.sup.2

or

    CH.sub.2 =CHC(R.sup.1)=CHR.sup.2

where

R¹ is hydrogen, methyl, ethyl or chlorine, and

R² is hydrogen, C₁ -C₁₅ alkyl, C₆ -C₁₂ aryl, or C₇ -C₁₈ alkaryl,

in the presence of a catalyst system which comprises

(a) organic solvent-soluble organonickel compound in which the nickel iszerovalent or divalent,

(b) hydrocarbylaluminum halide selected from the group consisting ofhydrocarbylaluminum chlorides and hydrocarbylaluminum bromides, and

(c) aryl phosphinite of the formula

    R.sup.3 R.sup.4 POR.sup.5

where

R³ and R⁴, alike or different, are phenyl or substituted phenylcontaining up to two substituents selected from the group consisting ofC₁ -C₆ alkyl, chlorine, bromine, iodine and fluorine, and

R⁵ is C₆ -C₁₂ aryl, or substituted C₆ -C₁₂ aryl containing up to twosubstituents selected from the group consisting of C₁ -C₆ alkyl, C₁ -C₆alkoxy, chlorine, bromine, iodine, fluorine, trifluoromethyl and di(C₁-C₆ alkyl) amino.

It is preferred, because the trans/cis-isomer ratio of the 1,4-dieneproduct is increased still further, to carry out the reaction in thepresence of a heteroorganoaluminum compound of the formula

    (R.sup.6).sub.a AlZ.sub.b

where

R⁶ is C₁ -C₆ alkyl, C₃ -C₆ cycloalkyl, C₇ -C₁₈ aralkyl, or C₆ -C₁₂ aryl,

Z is OR⁷, --NR⁸ (R⁹), or =NR¹⁰,

where

R⁷, r⁸, r⁹ and R¹⁰, alike or different, are C₁ -C₆ alkyl, C₃ -C₆cycloalkyl, C₇ -C₁₈ aralkyl, or C₆ -C₁₂ aryl,

a is 1 or 2,

b is 1 or 2, and

a+ b is 3,

except that when Z is =NR¹⁰,

a is 1,

b is 1,

a+ is 2, and

R⁶ can also be hydrogen.

The terms "trans" and "cis" 1,4-dienes refer to the isomerism about theC-4/C-5 bond. Where R¹ in the starting 1,3-diene is hydrogen, a transisomer has the configuration about the C-4/C-5 bond ##STR2## Where R¹ isan atom or a group other than hydrogen, the trans isomer has theconfiguration ##STR3## The cis isomer has the configuration ##STR4##respectively.

The term "aryl" refers to a group derived from a hydrocarbon containingat least one 6-membered aromatic hydrocarbon ring by removal of ahydrogen atom from a ring carbon.

The term "alkyl" refers to a group derived from a saturated aliphatichydrocarbon by removal of a hydrogen atom.

The term "cycloalkyl" refers to a group derived from a saturatedalicyclic hydrocarbon by removal of a hydrogen atom.

The term "aralkyl" refers to a group derived from aliphatic hydrocarbonhaving at least one aromatic substituent by removal of an aliphatichydrogen atom.

The term "alkaryl" refers to a group derived from aromatic hydrocarbonhaving at least one alkyl substituent by removal of an aryl hydrogenatom.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with this invention 1,4-dienes having a trans/cis-isomerratio of at least about 4:1 are prepared by the addition of ethylene to1,3-diene. Suitable 1,3-dienes for use in accordance with this inventioninclude 1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene,chloroprene, 1,3-dodecadiene, 1,3-nonadecadiene, 4-phenyl-1,3-butadiene,4-naphthyl-1,3-butadiene, 4-(4-tolyl)-1,3-butadiene, and 5-phenyl-1,3-pentadiene. The preferred 1,3-diene for reaction withethylene is 1,3-butadiene which gives as the product, 1,4-hexadiene, avery useful comonomer in the preparation of EPDM elastomers.

The reaction can be carried out either batchwise, semicontinuous orcontinuous. In the batch process, the reactants and the catalystcomponents are dissolved in an inert solvent, such as an aromatic oraliphatic hydrocarbon, or halogenated hydrocarbon. The concentration of1,3-diene in a batchwise reaction can be varied virtually withoutlimits, but it is convenient to use diene solutions which are about 1 toabout 4 molar. In a continuous process the diene itself can serve as asolvent.

The reaction is carried out in the presence of a catalyst systemcontaining an organic solvent-soluble organonickel compound in which thenickel is zerovalent or divalent. Suitable nickel compounds includenickel(O)bis(1,5-cyclooctadiene) complex, nickel tetracarbonyl,nickel(O)(1,5,9-dodecadiene) complex, nickel(O)(cyclooctatetraene)complex, nickel(II) acetylacetonate, nickel(II) cyclohexylbutyrate,dicrotylnickel(II), diallylnickel(II), dimethallylnickel(II), andcrotyl-, allyl-, and methallylnickel(II) dichloride, dibromide, anddiiodide. The preferred nickel compound isnickel(O)bis(1,5-cyclooctadiene).

The nickel compound concentration generally is maintained within therange of about 0.00001 to about 0.01 mole per liter. Below the lowerlimit the reaction does not proceed at a satisfactory rate, while abovethe upper limit the reaction is difficult to control, and appreciablepolymer formation is observed.

The catalyst system also contains a hydrocarbylaluminum chloride orbromide. Hydrocarbylaluminum halides which can be used in the process ofthis invention include alkylaluminum, arylaluminum, and aralkylaluminumhalides. The organic radical usually has 1 to about 12 carbon atoms, thepreferred number being 2 to about 6 carbon atoms. These preferredcompounds are readily available at moderate cost and have high catalyticactivity on a weight basis. Representative compounds includedialkylaluminum halides such as diethylaluminum chloride,dibutylaluminum chloride, diisobutylaluminum chloride anddipropylaluminum chloride; diarylaluminum halides such asdiphenylaluminum chloride and dinaphthylaluminum chloride;diaralkylaluminum halides such as dibenzylaluminum chloride anddi(p-methylbenzyl)-aluminum chloride; alkylaluminum dihalides such asethylaluminum dichloride, propylaluminum dichloride and isobutylaluminumdichloride; arylaluminum dihalides such as phenylaluminum dichloride andnaphthylaluminum dichloride; aralkylaluminum dihalides such asbenzylaluminum dichloride and p-methylbenzylaluminum dichloride; and thecorresponding dibromides. Usually, alkylaluminum dihalides are the mostreadily available and especially preferred compounds.

The amount of hydrocarbylaluminum halide present should be at leastequimolar with the nickel compound. Although a large molar excess of thehydrocarbylaluminum halide can be present, e.g., about 100:1, noadvantage is gained thereby. The preferred molar ratio of aluminum tonickel, at which the reaction is readily controlled, is about 3:1 toabout 10:1. In general, an increase in the aluminum/nickel ratio givesincreased conversions, but a lower trans/cis ratio.

The catalyst system also contains an aryl phosphinite of the formula

    R.sup.3 R.sub.4 POR.sup.5

as defined above, which forms a stable complex with the organonickelcompound. The ability of a phosphinite to form such a complex depends onseveral factors, including the phosphinite's basicity and stericeffects. It has been found that phosphinites of the above formulasatisfy all the requirements. Representative phosphinites includeunsubstituted aryl diphenylphosphinites such as

phenyl diphenylphosphinite,

2-naphthyl diphenylphosphinite,

1-naphthyl diphenylphosphinite and

4-biphenylyl diphenylphosphinite;

substituted aryl diphenylphosphinites such as

2-chlorophenyl diphenylphosphinite,

4-chlorophenyl diphenylphosphinite,

4-i-propylphenyl diphenylphosphinite,

2-methylphenyl diphenylphosphinite,

3-trifluoromethylphenyl diphenylphosphinite,

2-ethylphenyl diphenylphosphinite,

2-hexylphenyl diphenylphosphinite,

3-fluorophenyl diphenylphosphinite,

3-bromophenyl diphenylphosphinite,

3-iodophenyl diphenylphosphinite,

3-methylphenyl diphenylphosphinite,

3-i-propylphenyl diphenylphosphinite,

4-methoxyphenyl diphenylphosphinite,

2-methyl-4-methoxyphenyl diphenylphosphinite,

4-butoxyphenyl diphenylphosphinite,

4-(dimethylamino)phenyl diphenylphosphinite,

4-(diethylamino)phenyl diphenylphosphinite,

2-methyl-4-chlorophenyl diphenylphosphinite,

2,4-dimethylphenyl diphenylphosphinite,

2-methyl-4-methoxyphenyl diphenylphosphinite,

3,5-dichlorophenyl diphenylphosphinite,

4-hexyloxyphenyl diphenylphosphinite,

2-methyl-1-naphthyl diphenylphosphinite, and

2-chloro-1-naphthyl diphenylphosphinite;

and aryl di(substituted phenyl)phosphinites such as

phenyl bis(2-methylphenyl)phosphinite,

phenyl bis(4-bromophenyl)phosphinite,

phenyl bis(2-methyl-4-chlorophenyl)phosphinite,

phenyl bis(4-i-propylphenyl)phosphinite,

phenyl bis(2,4-dimethylphenyl)phosphinite,

phenyl bis(4-hexylphenyl)phosphinite,

phenyl bis(4-fluorophenyl)phosphinite,

phenyl bis(4-iodophenyl)phosphinite,

2-chlorophenyl bis(4-chlorophenyl)phosphinite, and

2-naphthyl bis(4-chlorophenyl)phosphinite.

The preferred aryl phosphinites are substituted phenyldiphenylphosphinites.

In addition to the hydrocarbylaluminum halide, or as a replacement forpart of the hydrocarbylaluminum halide present in the reaction medium, aheteroorganoaluminum compound of the formula (R⁶)_(a) AlZ_(b), asdefined above, optionally can also be present in the solution. Thepresence of such a heteroorganoaluminum compound, which has a higherbasicity than the hydrocarbylaluminum halide, further increases thetrans/cis ratio of the 1,4-diene produced by the process of thisinvention. Representative heteroorganoaluminum compounds in which Z is-OR⁷ include dialkylaluminum alkoxides such as diethylaluminum ethoxide,dimethylaluminum ethoxide and diisobutylaluminum methoxide;dialkylaluminum aryloxides such as diethylaluminum phenoxide anddiisobutylaluminum phenoxide; dialkylaluminum aralkoxides such asdipropylaluminum benzyloxide and diethylaluminum benzyloxide;diarylaluminum alkoxides such as diphenylaluminum ethoxide anddi(p-tolylaluminum) ethoxide; diaralkylaluminum alkoxides such asdibenzylaluminum ethoxide and dibenzylaluminum methoxide; alkylaluminumdialkoxides such as methylaluminum dipropoxide, and isobutylaluminumdiisopropoxide; cycloalkylaluminum dialkoxides such ascyclohexylaluminum dimethoxide; arylaluminum dialkoxides such asphenylaluminum dimethoxide and p-tolylaluminum diethoxide; andaralkylaluminum dialkoxides such as benzylaluminum diethoxide andbenzylaluminum dipropoxide.

Representative compounds in which Z is --NR⁸ (R⁹) includedialkylaluminum N,N-dialkylamides such as diethylaluminumN,N-dimethylamide, dibutylaluminum N,N-dimethylamide, dipropylaluminumN,N-diethylamide and dibutylaluminum N,N-diisopropylamide; alkylaluminumN,N,N',N'-tetraalkyldiamides such as ethylaluminumN,N,N',N'-tetraethyldiamide, and methylaluminumN,N,N',N'-tetramethyldiamide; cycloalkylaluminumN,N,N',N'-tetraalkyldiamides such as cyclohexylaluminumN,N,N',N'-tetramethyldiamide; arylaluminum N,N,N',N'-tetraalkyldiamidessuch as phenylaluminum N,N,N',N'-tetramethyldiamide and p-tolylaluminumN,N,N',N'-tetramethyldiamide; and aralkylaluminumN,N,N',N'-tetraalkyldiamides such as benzylaluminumN,N,N',N'-tetramethyldiamide and benzylaluminumN,N,N',N'-tetraethyldiamide.

Representative compounds in which Z is =NR¹⁰ include, for example,alkylaluminum alkylimides such as ethylaluminum ethylimide,ethylaluminum methylimide, butylaluminum ethylimide andisopropylaluminum methylimide; alkylaluminum aralkylimides such asisopropylaluminum benzylimide and ethylaluminum benzylimide;cycloalkylaluminum alkylimides such as cyclohexylaluminum methylimide;arylaluminum alkylimides such as phenylaluminum methylimide andphenylaluminum ethylimide; aralkylaluminum arylimides such asbenzylaluminum phenylimide and benzylaluminum p-tolylimide;alkylaluminum arylimides such as methylaluminum phenylimide,ethylaluminum phenylimide and isobutylaluminum phenylimide; andarylaluminum arylimides such as phenylaluminum phenylimide andp-tolylaluminum phenylimide. The preferred heteroorganoaluminumcompounds are the dialkylaluminum alkoxides.

The amount of the heteroorganoaluminum compound used is based on theconcentration of the hydrocarbylaluminum halide in the solution.Usually, the concentration of heteroorganoaluminum compound is chosen sothat there are at least about 0.6 Z group present in solution for eachthree halogen atoms. It is not practical to increase the concentrationof the heteroorganoaluminum compound beyond the ratio of about 1.2 Z foreach halogen atom because the reaction rate is thereby unduly decreased.The preferred concentration range is about 0.2 to about 1 Z group foreach halogen atom.

The aryl phosphinite is usually either premixed with the nickel compoundor added separately. When the reaction is carried out batchwise, thehydrocarbylaluminum halide is usually added last. When aheteroorganoaluminum compound is employed, it is convenient to premix itwith the hydrocarbylaluminum halide. The amount of aryl phosphinitepresent in the catalytic system should be about equimolar with thenickel compound. Although an excess quantity of aryl phosphinite can bepresent, it is undesirable because it can change the acidity of themedium to the extent that the addition reaction is impaired orprevented. A proper balance must therefore be maintained between theconcentration of the aryl phosphinite and the acidic hydrocarbylaluminumhalide.

The reaction is carried out within the temperature range of about -20°to about 100° C. The most suitable temperature range is from about 0° toabout 40° C. since the isomer ratio can best be controlled under theseconditions and the reaction rate is satisfactory. At highertemperatures, more polymeric material may be formed. Generally,formation of polymeric material cannot be completely avoided. It ispossible, however, to keep it at a low level of 3 to 4%, or at mostabout 20% of the total product. So long as the total conversion israised no higher than about 40-60%, formation of polymeric materialsdoes not exceed these limits. Above this conversion range, not only is ahigher proportion of polymeric material formed, but also otherby-products often increase. The reaction is exothermic, and the reactorpreferably is cooled to control the temperature.

The reaction is carried out at pressures from about atmospheric up toabout 10,000 psig. The most suitable range for both the batch andcontinuous processes is about 15 to about 500 psig because good ratesare obtained within this range over a wide range of temperatures. Atpressures above 10,000 psig the reaction tends to proceed faster and maylead to more polymeric materials, while at pressures below atmosphericthe reaction rate is often too slow to be practical. In practice, abatch reactor is maintained under a constant ethylene pressure byleaving the ethylene supply lines open during the reaction. The amountof ethylene which is dissolved in the reaction medium depends on thepartial pressure of ethylene gas above the solution. Ethylene which isconsumed in the addition reaction is constantly replaced. In thecontinuous process it is advantageous to use pressures at the higher endof the preferred range with as short residence times as practical forthe desired conversion of 1,3-diene.

Prior to the reaction, the reactor is swept with a dry inert gas. Theaddition of ethylene to the 1,3-diene is also carried out in a dry inertatmosphere. Because of its low cost and ready availability, nitrogen isthe preferred inert gas. In a batch reactor a small amount of nitrogenmay be present, its partial pressure usually being no more than about 10psig. In a continuous reactor the nitrogen originally present iseventually completely displaced by the stream of ethylene.

When the reaction has reached the desired conversion level, theorganoaluminum compounds present in the solution are decomposed byadding a compound having an active hydrogen, such as an alcohol, phenol,or even water. It is preferred to use an alcohol. The reaction mixtureis distilled to separate the reaction products from the monomers and thecatalyst. Alternatively, the reaction can be stopped by cooling to about-20° C., and the monomers can be removed at this low temperature bydistillation at reduced pressure. In either case, the monomers can berecycled. When the reaction is stopped by cooling, the catalyst can alsobe recycled. It is usually necessary in such a case to add moreorganoaluminum compounds, while it is not necessary to replace thenickel compound, since it does not undergo decomposition in thereaction.

1,4-Dienes with a high trans-isomer content, which are prepared by theprocess of the present invention, are particularly useful in thepreparation of ethylene/propylene/unconjugated diene terpolymers (EPDMpolymers), in which they supply vulcanization sites.

EXAMPLES OF THE INVENTION

The following examples illustrate the process of this invention. Allparts and percentages are by weight and all degrees are Centigradeunless otherwise stated.

EXAMPLE 1

The nickel (O)bis(cyclooctadiene) used in this example was prepared bythe reaction of nickel bis(acetylacetonate) with cyclooctadiene,butadiene, and aluminum triethyl as described by Collette and Su in U.S.Pat. No. 3,565,967.

The reaction of ethylene with 1,3-butadiene was carried out as follows:

The reaction vessel consisted of a glass lower section and a stainlesssteel upper section fitted with tubes through which reactants could beadded to and products withdrawn from the glass section. The vessel wasequipped with a stirrer and the two sections were clamped together usinga gasket of Teflon® fluorocarbon polymer. It was immersed in water at26°, evacuated, and pressured to 30 psig with ethylene. Four solutionswere delivered to the reactor: (1) 20% 1,3-butadiene in toluene at therate of 81 ml per hr; (2) a 0.1 M solution ofnickel(0)bis(cyclooctadiene) in toluene at the rate of 1 ml per hr; (3)a 0.1 M solution of phenyl diphenylphosphinite in toluene at the rate of1 ml per hr; and (4) a toluene solution which was 1 M in ethylaluminumdichloride and 1.8 M in diethylaluminum ethoxide at the rate of 1 ml perhr. Ethylene was added continuously so that the total pressure withinthe reactor was maintained at 30 psig.

When 15 ml of liquid had accumulated in the reactor, liquid waswithdrawn continuously at the rate of about 84 ml per hour to maintainthe volume of solution in the reactor at 15 ml. The reaction wascontinued for 5 hours. About 1% of methanol was added continuously tothe product as it discharged from the reactor to destroy the catalystand arrest further reaction.

Periodic gas liquid chromatographic (GLC) analysis of the product wascarried out on a 1/8" × 12' column of 20% cyanoethyl silicone (GE XE-60)on an 80-100 mesh diatomite support. The column was programmed for arise in temperature from 35° to 50° over an 11-minute period, and it wasthen programmed to 200° at a rate of 40°/min. The helium flow rate was40 ml/min. The analysis showed that up to 10% of the butadiene wasconverted to 1,4-hexadiene in which the ratio of trans-1,4-hexadiene tocis-1,4-hexadiene was 4.2:1 which is equivalent to a trans-isomercontent of 81%.

EXAMPLE 2

Using the same equipment and the same general procedure as in Example 1,four solutions: (1) 20% 1,3-butadiene in toluene at the rate of 88 mlper hr; (2) 0.1 M nickel(O)bis(cyclooctadiene) in toluene at the rate of0.9 ml per hr; (3) 0.1 M 2-chlorophenyl diphenylphosphinite in tolueneat the rate of 0.9 ml per hr; and (4) a toluene solution 1 M inethylaluminum dichloride and 1.8 M in diethylaluminum ethoxide at therate of 0.9 ml per hr, were added simultaneously to the reactor at 25°and under ethylene at a total pressure of 30 psig.

The volume of liquid maintained in the reactor was 20 ml and reactionextended over 3 hr. Samples were analyzed by GLC analysis at 30 minintervals. The extent of conversion of butadiene to 1,4-hexadiene rangedfrom 12% to 25% and the trans-1,4-hexadiene/cis-1,4-hexadiene ratio from4.1/1 to 4.3/1.

EXAMPLE 3

Using the equipment and procedure of Example 1, four solutions: (1) 20%1,3-butadiene in toluene at the rate of 47 ml per hr; (2) 0.1 Mnickel(O)bis(cyclooctadiene) in toluene at the rate of 1.0 ml/hr; (3)0.1 M phenyl diphenylphosphinite in toluene at the rate of 1.0 ml/hr;(4) a toluene solution which was 1 M in isobutylaluminum dichloride and1.8 M in diethylaluminum ethoxide at the rate of 1 ml per hr, were addedsimultaneously to the reactor at 0° under ethylene at a total pressureof 30 psig.

The volume of liquid maintained in the reactor was 20 ml and thereaction extended over 4 hours. Samples were analyzed by GLC analysis at30 min intervals. The extent of conversion of butadiene to 1,4-hexadieneranged from 5% to 15% and the trans/cis-isomer ratio from 5.8/1 to6.4/1.

EXAMPLES 4-13

A 30-ml glass reaction vessel containing a magnetized stirrer bar waspurged with nitrogen, chilled to -80° and charged, under nitrogen, withreactants in the following sequence: (1) 10 ml of 20% 1,3-butadiene intoluene; (2) 0.1 ml of 0.066 M aryl diphenylphosphinite in toluene; (3)0.2 ml of 0.033 M nickel(O)bis(cyclooctadiene) in toluene; and (4) 0.1ml of a toluene solution that was 0.25 M in isobutylaluminum dichlorideand 0.1 M in diethylaluminum ethoxide. The flask was immersed in liquidnitrogen to freeze the reaction mixture and evacuated. Twentymilliliters of ethylene gas was admitted, the reactor was immersed in awater bath at 30°, and additional ethylene was admitted at a pressure of30 psig with stirring. After 30 minutes the valve through which ethylenewas admitted was closed and the reaction mixture was chilled to -80°.The reactor was then opened and about 1 ml of methanol was added toarrest the catalyst. The reaction product was analyzed by GLC analysis.The specific aryl diphenylphosphinite used and the results aresummarized in Table I.

                                      TABLE I                                     __________________________________________________________________________                                 % Conversion                                                                             1,4-Hexadiene                                                      (1,3-Butadiene to                                                                        trans/cis Isomer                      Example                                                                            Aryl Diphenylphosphinite                                                                              1,4-Hexadienes)                                                                          Ratio                                 __________________________________________________________________________    4    Phenyl diphenylphosphinite                                                                            25         4.56                                  5    4-Isopropylphenyl diphenylphosphinite                                                                 20         4.20                                  6    2-Methylphenyl diphenylphosphinite                                                                    25         4.15                                  7    3-Trifluoromethylphenyl diphenylphosphinite                                                           20         4.33                                  8    2-Ethylphenyl diphenylphosphinite                                                                     20         4.23                                  9    2-Chlorophenyl diphenylphosphinite                                                                    25         5.13                                  10   3-Fluorophenyl diphenylphosphinite                                                                    20         4.88                                  11   3-Methylphenyl diphenylphosphinite                                                                    20         4.40                                  12   3-Isopropylphenyl diphenylphosphinite                                                                 20         4.36                                  13   2-Naphthyl diphenylphosphinite                                                                        20         4.06                                  __________________________________________________________________________

EXAMPLES 14-16

The general procedure was that described for Examples 4-13 except thatthe toluene solution, 0.25 M in isobutylaluminum dichloride and 0.1 M indiethylaluminum ethoxide, was replaced with 0.1 ml of a toluene solutionthat was 0.15 M in isobutylaluminum dichloride. The results aresummarized in Table II.

                                      Table II                                    __________________________________________________________________________                            % Conversion                                                                             1,4-Hexadiene                                                      (1,3-Butadiene to                                                                        trans/cis Isomer                           Example                                                                            Aryl Diphenylphosphinite                                                                         1,4-Hexadienes)                                                                          Ratio                                      __________________________________________________________________________    14   4-Chlorophenyl diphenylphosphinite                                                               20         4.19                                       15   Phenyl diphenylphosphinite                                                                       20         4.30                                       16   2-Chlorophenyl diphenylphosphinite                                                               20         4.94                                       __________________________________________________________________________

EXAMPLE 17

A 30-ml glass reactor containing a magnetized stirrer bar was purgedwith nitrogen, chilled to -80° and charged, under nitrogen, withreactants in the following sequence: (1) 10 ml of 20% 1,3-butadiene intoluene; (2) 0.1 ml of 0.066 M phenyl diphenylphosphinite in toluene;(3) 0.2 ml of 0.033 M nickel bis(acetylacetonate) in toluene; and (4)0.4 ml of a toluene solution which was 0.15 M in isobutylaluminumdichloride and 0.15 M in diethylaluminum ethoxide. The flask wasimmersed in liquid nitrogen to freeze the reaction mixture, andevacuated. Twenty milliliters of ethylene gas was admitted, the reactorwas immersed in a water bath at 30°, and additional ethylene wasadmitted at a pressure of 70 psig with stirring. After 30 minutes thevalve through which ethylene was admitted was closed and the reactionmixture was chilled to -80°. The reactor was then opened and about 1 mlof methanol was added to arrest the catalyst. GLC analysis showed that15% of the butadiene had been converted to 1,4-hexadiene with atrans/cis-isomer ratio of 4.15.

I claim:
 1. Method of preparing 1,4-diene of high trans-isomer content which comprises contacting ethylene with 1,3-diene of the formula

    CH.sub.2 =C(R.sup.1)CH=CHR.sup.2

or

    CH.sub.2 =CHC(R.sup.1)=CHR.sup.2

where R¹ is hydrogen, methyl, ethyl or chlorine, and R² is hydrogen, C₁ -C₁₅ alkyl, C₆ -C₁₂ aryl, or C₇ -C₁₈ alkaryl,in the presence of a catalyst system which comprises (a) organic solvent-soluble organonickel compound in which the nickel is zerovalent or divalent, (b) hydrocarbylaluminum halide selected from the group consisting of hydrocarbylaluminum chlorides and hydrocarbylaluminum bromides, and (c) aryl phosphinite of the formula

    R.sup.3 R.sup.4 POR.sup.5

where R³ and R⁴, alike or different, are phenyl, or substituted phenyl containing up to two substituents selected from the group consisting of C₁ -C₆ alkyl, chlorine, fluorine, bromine and iodine, and R⁵ is C₆ -C₁₂ aryl or substituted C₆ -C₁₂ aryl containing up to two substituents selected from the group consisting of C₁ -C₆ alkyl, C₁ -C₆ alkoxy, chlorine, bromine, iodine, fluorine, trifluoromethyl and di(C₁ -C₆ alkyl) amino.
 2. The method of claim 1 in which the catalyst system also contains a heteroorganoaluminum compound of the formula

    (R.sup.6).sub.a AlZ.sub.b

where R⁶ is C₁ -C₆ alkyl, C₃ -C₆ cycloalkyl, C₇ -C₁₈ aralkyl, or C₆ -C₁₂ aryl, Z is OR⁷, --NR⁸ (R⁹), or =NR¹⁰ where R⁷, r⁸, r⁹ and R¹⁰, alike or different, are C₁ -C₆ alkyl, C₃ -C₆ cycloalkyl, C₇ -18 aralkyl, or C₆ -C₁₂ aryl, a is 1 or 2, b is 1 or 2, and a+ b is 3,except that when Z is =NR¹⁰, a is 1, b is 1, a+ b is 2, and R⁶ can also be hydrogen.
 3. Method of preparing 1,4-diene of high trans-isomer content which comprises contacting ethylene with 1,3-diene of the formula

    CH.sub.2 =C(R.sup.1)CH=CHR.sup.2

or

    CH.sub.2 =CHC(R.sup.1)=CHR.sup.2

where R¹ is hydrogen, methyl or ethyl, and R² is hydrogen or C₁ -C₁₅ alkyl,in the presence of a catalyst system which comprises (a) organic solvent-soluble organonickel compound in which the nickel is zerovalent or divalent, (b) hydrocarbylaluminum halide selected from the group consisting of hydrocarbylaluminum chlorides and hydrocarbylaluminum bromides, and (c) aryl phosphinite of the formula

    R.sup.3 R.sup.4 POR.sup.5

where R³ and R⁴, alike or different, are phenyl, or substituted phenyl containing up to two substituents selected from the group consisting of C₁ -C₆ alkyl, chlorine, fluorine, bromine and iodine, and R⁵ is C₆ -C₁₂ aryl, or substituted C₆ -C₁₂ aryl containing up to two substituents selected from the group consisting of C₁ -C₆ alkyl, C₁ -C₆ alkoxy, chlorine, bromine, iodine, fluorine, trifluoromethyl and di(C₁ -C₆ alkyl)amino.
 4. The method of claim 3 in which the 1,3-diene is 1,3-butadiene.
 5. The method of claim 4 in which the hydrocarbylaluminum halide is alkylaluminum dihalide.
 6. The method of claim 5 in which the aryl phosphinite is a substituted phenyl diphenylphosphinite.
 7. The method of claim 6 in which the organonickel compound is nickel(O)bis(cyclooctadiene).
 8. The method of claim 3 in which the catalyst system also contains a heteroorganoaluminum compound of the formula

    (R.sup.6).sub.a AlZ.sub.b

where R⁶ is C₁ -C₆ alkyl, C₃ -C₆ cycloalkyl, C₇ -C₁₈ aralkyl, or C₆ -C₁₂ aryl, Z is OR⁷, --NR⁸ (R⁹), or =NR¹⁰ where R⁷, r⁸, r⁹ and R¹⁰, alike or different, are C₁ -C₆ alkyl, C₃ -C₆ cycloalkyl, C₇ -18 aralkyl, or C₆ -C₁₂ aryl, a is 1 or 2, b is 1 or 2, and a+ b is 3,except that when Z is =NR¹⁰, a is 1, b is 1, a+ b is 2, and R⁶ can also be hydrogen.
 9. The method of claim 8 in which the 1,3-diene is 1,3-butadiene.
 10. The method of claim 9 in which the hydrocarbylaluminum halide is alkylaluminum dihalide.
 11. The method of claim 10 in which the aryl phosphinite is a substituted phenyl diphenylphosphinite.
 12. The method of claim 11 in which the organonickel compound is nickel(O)bis(cyclooctadiene). 